Personalized Medicine Promises Tailor-Made Diagnoses, Treatments

Stefan Lovgren
for National Geographic News
October 18, 2006
Imagine visiting your doctor for an annual exam—only this time the checkup begins not with a physical but with a routine sequencing of your genome.

Using information from the test, your physician not only diagnoses the diseases you are most susceptible to but also selects the types and doses of medication best suited to help you combat the maladies.

It's called personalized medicine. And no, it doesn't mean your doctor will be extra kind or personable.

The term broadly refers to the detection, treatment, and prevention of diseases based on a person's unique genetic makeup, and many people believe it will revolutionize health care.

"When you go to your physician ten years from now virtually all of the decisions about diagnosis and treatment will be based on individual information about your particular circumstance as opposed to a more general kind of approach to lots of other people in your general circumstance," said genome expert Francis Collins.

Collins is director of the National Human Genome Research Institute, which is part of the National Institutes of Health (NIH) in Bethesda, Maryland.

Tailored Treatment

Collins led the international effort to sequence the human genome, which was completed in 2003. That effort was followed by the creation of a map of human genetic variation. (Related: "Human Genome Shows Proof of Recent Evolution, Survey Finds" [March 8, 2006].)

The genome contains tens of thousands of genes, which code for proteins and other molecules that make life possible. (Get an overview of human genetics.)

Although there are some three billion "letters" in the human DNA code, 99.9 percent are identical between any two people. The small remaining differences hold clues about why people tend to develop particular diseases.

"We now have the technology to assess in people with disease, versus those who don't have the disease, which of those [genetic] variances seem to be overrepresented," Collins said.

"We are on the brink of discovering what are the hereditary factors in diabetes, heart disease, in the common cancers, high blood pressure, asthma, mental illness—virtually any disease you can think of that tends to run in families."

The genetic variations can be used to identify susceptibility to a particular disease and to pinpoint targets for drug treatments.

Currently drug courses are often ineffective. Physicians may have to prescribe several different treatments before identifying one that works.

"Personalized medicine is about changing the medical paradigm," said Edward Abrahams, executive director of the Personalized Medicine Coalition in Washington, D.C. "It promises to replace trial-and-error medicine with a more targeted get-it-right-the-first-time approach."

Many cancer patients can already use targeted drugs such as Novartis's Gleevec and Genentech's Tarceva that are known to work better in people with certain genetic profiles.

And a study published recently in the Journal of the American Medical Association showed that variations in one particular gene can predict which patients will respond to antidepressant drugs such as Eli Lilly's Prozac.

No Easy Feat

But personalized medicine still faces huge obstacles. Genetic testing, for instance, is hugely expensive right now. It currently costs millions of dollars to sequence one complete human genome.

Scientists are optimistic, however, that in as little as five years the cost could be less than a thousand U.S. dollars.

The Santa Monica, California-based X Prize Foundation recently announced a ten-million-dollar reward to the first company that can process the genetic codes of a hundred people in just ten days. (Related: "SpaceShipOne Wins Ten-Million-Dollar X Prize" [October 4, 2004].)

And the National Human Genome Research Institute has announced grant awards of more than U.S. $13 million to speed the development of innovative sequencing technologies that reduce the cost of DNA sequencing.

"The science is there, but the technology needs to come into place that brings the cost down," Abrahams, of the Personalized Medicine Coalition, said.

Today's Science

Collins, of the NIH, says that there are still ways to apply individualized medicine even without having a person's entire genome sequence.

Researchers can focus on specific places in the genome where they know there are genetic variations between people that carry a particular risk for disease, he says.

"You would do what's called genotyping," he said, "assessing spelling in a particular place on a chromosome where you know something important resides. We can already do any genotype on a particular DNA sequence for pennies or less."

Perhaps a more significant obstacle, Collins says, is to educate both physicians and patients about the use of sophisticated genetic tests.

Personalized medicine doesn't mean that "doctors are going to say, OK, you have this DNA 'spelling' so you're going to get cancer of the colon on your 43rd birthday," he said.

"Instead, the [genetic variations] are going to be statistical risk predictors. But these can be extremely useful in allowing people to practice their own more individualized preventive medicine.

Mixed Reponses

But many people have strong concerns about how genetic information should be used.

If genetic testing reveals a patient's predisposition to a certain condition, insurance companies could, for example, use that information to deny the patient health coverage.

A legislative bill prohibiting the use of genetic information in insurance and employment decisions has already passed the U.S. Senate but remains stuck in the House of Representatives.

What's more, a recent survey conducted by Research!America, a medical research advocacy group based in Alexandria, Virginia, showed that only one-third of Americans have heard the term "personalized medicine."

Once the term was defined for them, more than 80 percent of respondents said they believe increased availability of personalized medicine will improve doctors' abilities to diagnose diseases and evaluate a patient's risk for disease.

"People are positive about the concepts of personalized medicine to the extent they've heard about it," said Mary Woolley, Research!America's president.

Survey results showed that almost seven out of every ten U.S. residents would be willing to have their genetics tested to help doctors diagnose and prevent disease.

"There is no limitation on diseases" that can be treated, said Stacie Propst, director of science policy for Research!America. "Almost everything has some genetic predisposition or some genetic transformation that happens—literally a fingerprint on every one of our conditions or diseases."

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